7MCH

Crystal structure of a single-chain E/F type bilin lyase-isomerase MpeQ in space group C2221

Summary for 7MCH

• Entry DOI: 10.2210/pdb7mch/pdb
• Related: 7MC4
• Descriptor: bilin lyase-isomerase (2 entities in total)
• Functional Keywords: bilin lyase-isomerase, lyase
• Biological source: Synechococcus sp. A15-62
• Total number of polymer chains: 2
• Total formula weight: 93357.93

Authors

Yang, X.,Kumarapperuma, I. (deposition date: 2021-04-02, release date: 2022-08-24, Last modification date: 2024-10-09)

Primary citation

Kumarapperuma, I.,Joseph, K.L.,Wang, C.,Biju, L.M.,Tom, I.P.,Weaver, K.D.,Grebert, T.,Partensky, F.,Schluchter, W.M.,Yang, X.
Crystal structure and molecular mechanism of an E/F type bilin lyase-isomerase.
Structure, 30:564-574.e3, 2022

PubMed Abstract: Chromophore attachment of the light-harvesting apparatus represents one of the most important post-translational modifications in photosynthetic cyanobacteria. Extensive pigment diversity of cyanobacteria critically depends on bilin lyases that covalently attach chemically distinct chromophores to phycobiliproteins. However, how bilin lyases catalyze bilin ligation reactions and how some lyases acquire additional isomerase abilities remain elusive at the molecular level. Here, we report the crystal structure of a representative bilin lyase-isomerase MpeQ. This structure has revealed a "question-mark" protein architecture that unambiguously establishes the active site conserved among the E/F-type bilin lyases. Based on structural, mutational, and modeling data, we demonstrate that stereoselectivity of the active site plays a critical role in conferring the isomerase activity of MpeQ. We further advance a tyrosine-mediated reaction scheme unifying different types of bilin lyases. These results suggest that lyases and isomerase actions of bilin lyases arise from two coupled molecular events of distinct origin.

PubMed: 35148828
DOI: 10.1016/j.str.2022.01.007

Experimental method

X-RAY DIFFRACTION (2.95 Å)